1. Field of the Invention
The present invention relates to a managing structure for an umbilical member of an industrial robot used with a working tool mounted thereon.
2. Description of the Related Art
An industrial robot (hereinafter referred to as simply a “robot”) has a working tool mounted at the forward end of the front arm thereof, and an umbilical member, containing one or more wires and tubes, is very frequently used to supply, to the working tool, materials including air, energy such as electricity, and signals. In such a case, the umbilical member is generally led to extend above the front arm of the robot to the working tool. FIG. 1 shows an example of such a prior art.
In FIG. 1, reference numeral 1 designates a robot controlled by a robot controller 2. A first wrist element 11 is provided at the forward end of a front arm 10 of the robot 1 so as to be rotatable about a first axis A extending in a longitudinal direction of the first wrist element 11. A second wrist element 12 is mounted on the first wrist element 11 as to be rotatable about a second axis B extending substantially perpendicular to the first axis A. A third wrist element 13 is mounted on the second wrist element 12 so as to be rotatable about a third axis C1 extending substantially perpendicular to the second axis B, and has a working tool H provided at the forward end flange portion thereof. A part (such as a support base) of the working tool H may double as the third wrist element 13.
In this case, the working tool H is a hand having suction pads. Reference numeral 3 designates an air supply/suction unit disposed outside the robot 1. An air tube 31 connected to the air supply/suction unit 3 merges at an appropriate point with a control cable 21 for supplying electric power and electrical signals, etc. and connects to a solenoid valve box 4. The air is supplied or removed through a tube (umbilical member) 7 arranged from the solenoid valve box 4 to the hand H. The robot controller 2 controls the air supply/suction unit 3 and the solenoid valve box 4 in a well-known manner to switch between the air supply to the suction pads of the hand H (i.e. the holding “off” mode) and the air suction (i.e. the holding “on” mode) from the suction pads of the hand H.
The problem posed in this case is that the rotation about the axes A, B, C1 during the operation of the robot 1 may cause the umbilical member 7 to contact with the body (the forward portion beyond the front arm 10) of the robot 1 or to wind around the wrist elements 11, 12 or be pulled strongly by the wrist elements 11, 12. This trend is especially conspicuous in the case where the operation range about the axis C1 is wide (about 360 degrees, for example). For example, in a handling robot system for transferring disordered objects from one pallet to another pallet and arranging them into order, it is generally true that the axes of the wrist elements of the robot maintain a predetermined arrangement and that only the rotation about the last axis (the axis C1) covers a wide range in order to set the objects in phase with each other. Therefore, the above problem is liable to occur in such a handling robot system.
To avoid this problem, in the prior art, a method was employed in which the umbilical member 7 was laid so as to extend away from the robot by a sufficiently large distance body as shown in FIG. 1 and was connected to the hand (working tool) H.
However, such an arrangement of the umbilical member 7 involves a risk that the behavior of the umbilical member 7 is unstable when the robot wrist elements rotates about the axes (especially about the third axis C1), thereby causing the umbilical member 7 to contact (interfere) with a part of the robot body (the forward portion beyond the front arm) or the peripheral devices to damage the umbilical member itself or the peripheral devices. Also, the umbilical member 7 contacting and rubbing other objects generates fine dust and deteriorates the working environment. To overcome this problem, a method is possible in which the motion of the umbilical member 7 is controlled elastically by using an L-shaped member 5 and an elastic member 6 to hang the umbilical member 7 above the front arm 10. However, this method cannot sufficiently prevent the interference. Further, a large burden is imposed on the wires and tubes by the bending or twisting.